Plug contactor



Nov. 7, 1 961 w. H. MAvlTY 'PLUG coNTAcToR Filed March 25, 1959 HWENTQR.

(Jlam H. Nav'ltY mf *Amd* United States Patent 3,008,118 PLUG CONTACTOR William H. Mavity, Camp Hill, Pa., assigner to AMP Incorporated, Harrisburg, Pa. Filed Mar. 25, 1959, Ser. No. 801,944 3 Claims. (Cl. 339-217) This invention relates to plug contactors for use with the plugboard or circuit connecting panel of an electrical calculating or accounting machine or the like, and more particularly to a spring detent system securing the plug from being pushed from the plugboard by ordinary pressures on the nose of the plug, but permitting withdrawal from the plugboard by a pull on the rear portions of the plug.

The detent systems of the prior plugs of the type described are of complex design, generally including multiple parts which are expensive in manufacture and to incorporate in assembly in the plug body. It is among the objects of the present invention to provide a spring detent system for such a plug embodied in a single piece of inexpensive material and simple design, which piece may easily and quickly be assembled in a plug body. Another object of the invention is the provision of a plug of the type described which is simple and economical in construction while being rugged in use and foolproof in operation.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the Adrawings in which there are shown and described several illustrative embodiments of the invention; it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention but are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURE 1 is a longitudinal section view of an embodiment of a plug contactor incorporating features of the present invention, the plug being fully inserted in a plugboard;

FIGURE 2 is a fragmentary longitudinal section view of the plug of FIGURE 1 illustrating the action of the spring detent system during insertion of the plug in a plugboard aperture;

FIGURE 3 is a View similar to FIGURE 2 in a further stage during insertion of the plug;

FIGURE 4 is an enlarged sectional view taken along line 4-4 of FIGURE 1;

FIGURE 5 is an enlarged sectional view taken along line 5-5 of FIGURE 1; and

FIGURE 6 is a view similar to FIGURE 1 illustrating a modied form of a plug contactor.

The particular type of plug contactor to which this invention relates is especially adapted for use in the plugboard Wiring system of an electrical accounting or calculating machine or the like, which system typically includes a xed plug board carrying a set of permanent contacts arranged in rows and columns. A movable plugboard removably carrying a corresponding set of plug contactors is arranged 'to bring the sets of Contact elements into engagement so as to complete the electrical circuits desired.

Referring now to FIGURES 1 through 5, a plurality of apertures 2 of plugboard 4 receives a set of plug contactors, such as the plug generally designated at 6, in an array each for interengaging at its projecting nose 8 3,008,118 Patented Nov. 7, 1961 a corresponding contact in the contact set of the fixed plugboard, not shown.

Plug 6 comprises a hollow cylindrical sleeve or shell 10 of a conductive metal, such as tin-plated brass, preferably rolled up from flat sheet stock into tubular form with a butt seam 12 extending longitudinally of the sleeve, FIGURE 4. At its rearward end, the left-hand end as viewed in FIGURE l, sleeve 10 is provided with integral means 14 by which the conductor 16 is mechanically and electrically attached to the plug. Preferably attaching means 14 is formed into a ferrule from an initially U-shaped cross-section configuration, the ferrule being tightly crimped around wire core 18 of the conductor, FIGURE 5, by cold forging techniques conventional in the art as illustrated, for example, in Patent No. 2,600,012, issued June l0, 1952, to James C. Macy. To take up any metal of the ferrule in excess of that required to encompass Wire core 18, and to align the wire core more nearly coincident with the plug axis, the anvil die, not shown, utilized in forming the crimp may have a central rib to form a longitudinally extending indentation 19 inthe bottom of the crimp.

An insulating sheath 20 of a suitable resin such as polyvinyl chloride preferably is molded around the rear end of the plug and adjacent portions of the insulation of conductor 16. Sheath 20 insulates the ferrule or attaching means 14 and supports the adjacent portion of conductor 16 to increase its resistance to bending fatigue While conveniently serving as a handle for manipulating the plug.

At the rearward end of the cylindrical body of sleeve 10 adjacent the forward end of sheath 20, an integral circumferential bead 22 is provided, the bead being disposed so as to engage the face of plugboard 4 adjacent edge portions of an aperture 2 to act as a stop for limiting movement of the plug into the plug board.

Forwardly, nose 8 smoothly converges to present a rounded tip except for a small opening 24 at the very tip in alignment with the longitudinal axis of the plug for purposes to be explained.

Disposed within sleeve 10 yto provide the spring detent system of the plug is a spring 26 which is arranged to render the plug capable of being relatively easily inserted and withdrawn by sheath 20 or conductor 1|6, but ordinarily incapable of being dislodged from the plugboard by forces applied to the nose of the plug except under very violent conditions where it may be preferred to lose the detent latch Irather than risk extensive damage to the plug or plugboard. In general, spring 26 may be formed of any spring material of any suitable cross-sectional configuration which is resistant to crumpling on axial loading, for example, steel piano wire.

As shown in FIGURE l, the forward portion of spring 26 is generally V-shaped, the bight 28 extending into opening 24 and presenting a smoothly rounded tip from which the legs 30 and 31 of the V extend for ia short distance in closely spaced relation axially of the plug and then diverge to merge smoothly into the forward legs 32 of V-shaped ear or detent portions 34 and 35 respectively. A pair of diametrically spaced longitudinal slots 36 and 37 in the forward portion of sleeve 10, and spaced from bead 22 a distance slightly greater than the plugboard thickness, provide openings through which detente 34 and 35 project for engaging behind the aperture edges on the front face `as bead 22 comes into abutment with the rear face of the plugboard.

The rear legs 38 and 39 of detents 34 and 35 extend laterally of the longitudinal axis of the plug for substantially parallel disposition relative to the plugboard face on insertion of the plug. The ends of legs 38 and 39 lead into short -segments 40 and 41 which run parallel to the plug axis `and adjacent the inside wall of sleeve 10 to dethereof with wire core 1S in ferrule means 14, FIGURES 1 and 5, so as to tix the longitudinal position of knees 44'and 45 adjacent the opposite wall of sleeve 10 from detents 34'and 35 respectively.

On assemblingthe plug, spring 26 is inserted through the rear of sleeve until detents 34 and 35 protrude through slots 36 and 37 as bight 28 enters opening 24, legs 30V and l31 being formed with an initial bias tending to open spring 26 slightly more than the diameter of sleeve 10 to assure protrusion of detents 34 and 35. The ends ott legs 46 and 47 are then laid along ferrule means 14, upon which wire core 18 may be crimped therein before the molding of sheath 20 as desired.

As thus constructed and assembled, each side of spring 26 rom'knees 44 and 45 to bight 28 in action is similar to that `of a bow spring, one end of which is anchored or xed in position and the other end being free to slide along `the plug axis in a defined path of travel which approximates the cord line of the bow that is, the line including the ends Vof the bow. Det-ents 34 and 35 are positioned at the point of greatest departure of the bow springs from their respective cord lines. For convenience in illustrating the spring action, reference will be made to one side only of spring 26, for example, the bow spring `from bight 28 to knee 44 including leg 30, detent 34, stop segment 40, and diagonal portion 42. On insertion of the plug the sloping forward leg 32 of detent 34 engages the edges of aperture 2, FIGURE 2, to initiate a camrning action tending to flatten or decrease the general curvature of the bow, ultimately resulting in the detent being fully depressed, FIGURE 3. As bead 22 engages the rear plugboard face, slot 36 passes out oi `aperture 2 permitting detent 34 to spring out of sleeve 10, FIGURE 1, whereupon lateral leg 38 is positioned along the front face of the plugboard thereby latching the plug. During this action the end of the bow dened by knee 44 remains substantially zfixed in position while the other end, atbight 28,l moves outwardly of openingy 24 on flattening the bow, but returns -to its initial position when the bow recovers on full insertion of the plug.

To withdraw the plug it is necessary only to pull rearwardly on cord l16 or sheath `2t) which applies an eccentric loading to the bow spring tending to flatten it, that is, the reaction of pulling lateral leg'38 against the front face of the plugboard tends to rotate detent 34 around knee 44. As the free end of the bow, or bight 28, is constrained to travel axially of the pl-ug, the loading and ree suitant llattening of the bow spring thus tends to depress detent 34. Furthermore, on rotation lateral leg 38 assumes an inclined aspect to the forward edge of aperture 2 producing a camming-in force component in addition tothe fcamming'inlluence had by rearward movement of the -forward edge of slot 36 relative to the sloping forward leg-32,' thusto ldepress detent 34 fully and allowing Withdrawal ofthe plug. In this connection it will be appreciated thatby` varying the slope, relative to the plug axis, of'legs 32-and' 33, theforce required to insent'the plug may be varied; andthat the force required to withdraw` theV plug relative tothe insertion yforce may be varied as desired by changing the length of diagonal portions. 42 and 43, or -by inclining leg portions 38 land 39 more or less from perpendicular relation relative to the plug l2x18'.

When anyy attempt is made to unseat the plug by pressure -lapplied to the nose, theeffect is simply to urige detents 34 and 35 'more forcefully into latching engagement withy the plugboard. This effect is achieved through any one-lof several modes'of' action. First, as to each bow spring defined by the sides of spring 26, any force applied to the plug nose has a major component at the free end of the bow, or bight 28, which acts in a direction along the cord line of the bow. Since the distal end of the bow is iixed, the only result can be a tendency to increase the curvature or buckle the bow furtherl outwardly, which is in a direction to sustain detents 34 and 35 in latching position. Alternatively, in order for detents 34 and 35 to be depressed it is necessary that, short of complete internal collapse of the spring, bight 28 moves outwardly of opening 24, as has been explained, which is contrary to the direction the applied force is urging it. Again, any force applied to bight 28 is directly transmitted along legs 30 and 31 to jam lateral legs38 and 39 more tightly against the plugboard face, from which it can be seen that substantial resistance to dislodgement of the plug will be offered even where the inside ends of the spring are not anchored to the plug sleeve.

From the foregoing it will be appreciated that bight 28 need not protrude in the rest position of spring 26 from nose 8 as shown, but may be flush to thesame effect. In addition, if it be assured that at least initially the edges of the plugboard aperture exert no inward camming component on the detents, as by arranging lateral legs 33and 39 to lie parallel to the plugboard face, or to have a slight reverse inclination, adequate strength of spring 26 assures destruction of the plug or the plugboard before the plug will unseat on pressure applied to the plug nose. Under' certain conditions of use, however, it may be desirable that the plug be released prior to its destruction, in which event lateral legs 3S and 39y may be slightly inclined to the plug axis as desired.

In the embodiment shown in FIGURE 6, the characteristics and configuration of the spring detent system are generally the same as that of the embodiment of FIGURE 1, like parts being correspondingly numbered but with a letter suiix. It will be noted, however, that segments 40a and 41a extend as far as possible rearwardly in sleeve 10a along the same side of the plug as detents 34a and 35a respectively. Short diagonal segments 42a and 43a lead the ends of the spring into ferrule attaching means 14a.

As thus constructed, the -xed'end of each bow spring merely has been transferred to the forward end of ferrule means y14a and nearer the plug axis. The spring, however, is simpler to form and to insert. Further, it is essentially immaterial where segments 40a and 41'a are caused to lie in sleeve 10a upon crimping the spring ends and wire core 18a in ferrule means 14a.

=From the foregoing, it will be seenthat the embodiments of the invention described-in detail are comprised of a minimum number of parts which may easily and quickly be assembled in achievement of the objectives aforesaid. Other embodiments,- of course, will occur to those skilled in the art. For example, it will be apparent that one side only of spring 26, providing a single detent 34or 35, may be employed wit-h good results.

I claim:

1. A plug contactor comprising a sleeve having a rounded front portion and a ferrule-means at the back portion for attaching a conductor wire to the plug, an opening in said front portion substantially coaxial with the longitudinal axis of the plugand a slot'in the. sidewall of said sleeve, stop means on the rear portion of said sleeve for Hunting movement oftthe contactor into a contactor-receiving aperture, and an integral detent spring disposed in said sleeve includinga generally arcuate forward portion having one end disposed adjacent the sidewall of said sleeve diametrically from said slot and the other end extending into said opening,- a V-shaped detent intermediate the length of said arcuate portion and biased to protrude through said slot, and a leg member extending rearwardly of said sleeve from said one end, the end of said leg member adapted to be disposed and xed with the conductor wire insaid ferrule means.

2. A plug `contaetor comprising a sleeve having a rounded nose, an opening in said nose substantially smaller in diameter than the sleeve and positioned coaxial with the longitudinal axis of the plug and a slot in the sidewall of said sleeve, and a wire detent spring disposed in said sleeve including a generally arcuate portion having one end extending into and slidahle in said opening, the other end of said arcuate portion being disposed against the internal sidewall of the sleeve at a point along a line diametrically located relative to said slot, a V-shaped detent intermediate the length of said arcuate portion and -biased to protrude through said slot, the rearward side of said detent relative to the plug nose extending substantially perpendicular to said axis, and a stop segment extending rearwardly in said sleeve integrally from said detent and engageable with the sidewall of said sleeve to` limit the protrusion of said detent.

3. A plug contactor comprising a sleeve having a rounded nose, an opening in said nose substantially smaller in diameter than the sleeve and positioned coaxial with 2O the longitudinal axis of the plug, a pair of diametric slots in the sidewalls of said sleeve, and a wire detent spring disposed in said sleeve including a generally V-shaped forward portion with the apex of the V dening a bight extending into said opening, the legs of the V adjacent said bight being slidable in said opening, a pair of generally V-shaped detents integral with the respective legs of the V and biased to protrude through said slots, stop segments extending rearwardly in said sleeve integrally from said detents and engageable with the sidewalls of said sleeve adjacent said slots respectively to limit the protrusion of said detents, and leg segments extending rearwardly and diagonally in said sleeve integrally from said stop segments to engage the `sleeve sidewalls diametrically from the slot through which the associated detents project.

References itetl in the file of this patent UNlTED STATES PATENTS 2,624,774 Cunningham Jan. 6, 1953 2,748,367 Schelke et al. May 29, 1956 2,787,771 Francis Apr. 2, 1957 FOREIGN PATENTS 64,979 Denmark Nov. 4, 1946 

